Effect of SPD processing on mechanical behavior and dynamic strain aging of an Al-Mg alloy in various deformation modes and wide strain rate range

This work focuses on the effect of grain size and deformation mode on mechanical behavior and dynamic strain aging (DSA) process in an Al5083 alloy. The UFG material with average grain size of 0.4 µm was produced by equal channel angular pressing with parallel channels (ECAP-PC) which resulted in dramatic improvement of mechanical strength while reducing tensile ductility of the alloy. Biaxial stretching formability of the UFG alloy is similar to that of its coarse-grained (CG) counterpart. Analysis of plastic flow in the strain rate range of 10−5-2.5·103 s−1 showed that DSA process occurs in both CG and UFG alloys in the strain rate range of 10−5-10−3 s−1, whereas it is suppressed at higher strain rates 10−1-2.5·103 s−1 due to lack of time for solute atoms to 'arrest' gliding dislocations. The ECAP-PC processing also modified the DSA process, reducing the absolute value of negative strain rate sensitivity and activity of localized plastic flow, as well as changing the type of flow serrations on the stress-strain curves. These observations are rationalized based on grain refinement and reduction of concentration of solute atoms in the grain refinement due to their segregations at grain boundaries, which occurs during severe plastic deformation of Al alloys. An effect of deformation mode on the DSA process is also reported.